Requirements and considerations
WebRTC
Cross-Origin Resource Sharing CORS
Yoy need to enable CORS if the sample webpage is not served from the same origin host URL as the API Gateway, see
Cross-Origin Resource Sharing (CORS) on page 23.
No WebRTC connection through a symmetric NAT firewall
WebRTC cannot create a connection through a symmetric NAT firewall without using a TURN (Traversal Using Relays
around NAT) server. Currently, the API Gateway does not support using a TURN server.
Check with your system administrator if you are behind a symmetric NAT firewall, or run the test described here: Am I
behind a Symmetric NAT?1.
In that case, a WebRTC connection is possible only within the symmetric NAT firewall, that is, both your browser and
the API Gateway must be behind the firewall.
WebRTC connection on a local network uses mDNS
To prevent private IP addresses from leaking from a local network when running WebRTC applications, modern
browsers by default send mDNS (multicast DNS) addresses as ICE Candidates to the signaling server.
API Gateway support for mDNS
The signaling server running in the API Gateway supports resolving mDNS addresses when running on a Windows
version with native support for mDNS.
Native support for mDNS was introduced in Windows version 1809 (October 2018) or later, and is available in any
recently updated Windows Server 2019 or Windows 10 installations, and all Windows Server 2022 and Windows 11
installations.
WebRTC connections across routers in a local network
mDNS relies on multicast which by default will not pass through routers. This means that in enterprise environments,
mDNS will fail in many cases:
lmDNS over wired Ethernet works on the same local network segment, but in more complex network solution
(most enterprise environments), mDNS will fail.
lmDNS over WiFi will only work on simple network configurations (as for wired networks). In configurations
with WiFi extender or Mesh networks, mDNS will likely fail.
The signaling server running in the API Gateway supports a workaround for connections across routers on a local
network. The signaling server will attempt to get the client's local IP network address from X-Forwarded-For and
1https://webrtchacks.com/symmetric-nat/
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